AL GS Gas System Contractor Exam Questions
and Correct Answers (Verified Answers) Plus
Rationale 2027 Q&A| Instant Download Pdf
1. Which component is primarily used to shut off the gas supply to
an individual appliance?
a. Gas meter
b. Pressure regulator
c. Appliance shutoff valve
d. Vent connector
Rationale: An appliance shutoff valve allows the gas supply to a specific
appliance to be isolated for installation, maintenance, or emergency
service without shutting off the entire building's gas supply.
2. What is the primary purpose of a gas pressure regulator?
a. Increase gas temperature
b. Reduce and control gas pressure
c. Remove moisture from combustion air
d. Measure gas consumption
,Rationale: Gas regulators reduce incoming gas pressure to an
appropriate downstream pressure and maintain that pressure within an
acceptable range as demand changes.
3. Which material is commonly approved for underground gas piping
when properly installed?
a. PVC water pipe
b. ABS drain pipe
c. Approved polyethylene gas piping
d. Copper flashing
Rationale: Polyethylene gas pipe is commonly used for underground
fuel-gas distribution systems when it is specifically manufactured and
approved for gas service and installed using approved methods.
4. Why must gas piping be properly supported?
a. To increase gas pressure
b. To reduce pipe diameter
c. To prevent sagging, movement, and mechanical damage
d. To eliminate the need for shutoff valves
Rationale: Proper supports keep the piping aligned and protect it from
excessive strain, vibration, and physical damage that could compromise
the gas system.
, 5. What is the primary hazard associated with an uncontrolled
natural gas leak?
a. Freezing of the pipe
b. Water contamination
c. Fire or explosion
d. Excessive water pressure
Rationale: Natural gas can accumulate in an enclosed area and form a
combustible mixture with air. An ignition source can then cause a fire or
explosion.
6. Before working on an existing gas piping system, what should be
done first?
a. Increase the operating pressure
b. Remove the appliance vent
c. Shut off and isolate the gas supply as appropriate
d. Open all appliance burners
Rationale: Isolating the gas supply reduces the risk of uncontrolled gas
release while piping, valves, regulators, or appliances are being
serviced.
7. What is the purpose of a gas piping pressure test?
, a. Determine the color of the pipe
b. Measure appliance efficiency
c. Verify that the piping system is free from unacceptable leakage
d. Determine the age of the gas meter
Rationale: Pressure testing provides a method for verifying the integrity
of gas piping before it is placed into service or after modifications have
been made.
8. Which instrument is commonly used to measure gas pressure?
a. Thermocouple
b. Ammeter
c. Manometer
d. Hydrometer
Rationale: A manometer measures relatively low gas pressures and is
commonly used during gas-system testing, commissioning, and
troubleshooting.
9. What is the purpose of a sediment trap in a fuel-gas system?
a. Increase gas pressure
b. Help collect debris and condensate before they enter an appliance
gas control
and Correct Answers (Verified Answers) Plus
Rationale 2027 Q&A| Instant Download Pdf
1. Which component is primarily used to shut off the gas supply to
an individual appliance?
a. Gas meter
b. Pressure regulator
c. Appliance shutoff valve
d. Vent connector
Rationale: An appliance shutoff valve allows the gas supply to a specific
appliance to be isolated for installation, maintenance, or emergency
service without shutting off the entire building's gas supply.
2. What is the primary purpose of a gas pressure regulator?
a. Increase gas temperature
b. Reduce and control gas pressure
c. Remove moisture from combustion air
d. Measure gas consumption
,Rationale: Gas regulators reduce incoming gas pressure to an
appropriate downstream pressure and maintain that pressure within an
acceptable range as demand changes.
3. Which material is commonly approved for underground gas piping
when properly installed?
a. PVC water pipe
b. ABS drain pipe
c. Approved polyethylene gas piping
d. Copper flashing
Rationale: Polyethylene gas pipe is commonly used for underground
fuel-gas distribution systems when it is specifically manufactured and
approved for gas service and installed using approved methods.
4. Why must gas piping be properly supported?
a. To increase gas pressure
b. To reduce pipe diameter
c. To prevent sagging, movement, and mechanical damage
d. To eliminate the need for shutoff valves
Rationale: Proper supports keep the piping aligned and protect it from
excessive strain, vibration, and physical damage that could compromise
the gas system.
, 5. What is the primary hazard associated with an uncontrolled
natural gas leak?
a. Freezing of the pipe
b. Water contamination
c. Fire or explosion
d. Excessive water pressure
Rationale: Natural gas can accumulate in an enclosed area and form a
combustible mixture with air. An ignition source can then cause a fire or
explosion.
6. Before working on an existing gas piping system, what should be
done first?
a. Increase the operating pressure
b. Remove the appliance vent
c. Shut off and isolate the gas supply as appropriate
d. Open all appliance burners
Rationale: Isolating the gas supply reduces the risk of uncontrolled gas
release while piping, valves, regulators, or appliances are being
serviced.
7. What is the purpose of a gas piping pressure test?
, a. Determine the color of the pipe
b. Measure appliance efficiency
c. Verify that the piping system is free from unacceptable leakage
d. Determine the age of the gas meter
Rationale: Pressure testing provides a method for verifying the integrity
of gas piping before it is placed into service or after modifications have
been made.
8. Which instrument is commonly used to measure gas pressure?
a. Thermocouple
b. Ammeter
c. Manometer
d. Hydrometer
Rationale: A manometer measures relatively low gas pressures and is
commonly used during gas-system testing, commissioning, and
troubleshooting.
9. What is the purpose of a sediment trap in a fuel-gas system?
a. Increase gas pressure
b. Help collect debris and condensate before they enter an appliance
gas control
